Hand grinder with a drive motor, designed as a compressed-air motor

ABSTRACT

A hand grinder driven by a compressed-air motor has attached on the work-engaging side thereof a hollow workplate, which carries on its underside a cover plate under which bears an abrasive sheet. Suction for the removal of grindings is provided by means of a duct terminating at one end at the handle in a connection for a suction device and passing through the grinder to the hollow workplate, from which openings to the grinding surface pass through both the cover plate and the abrasive sheet.

United States Patent 1191 Attinger Dec. 17, 1974 DESIGNED AS A COMPRESSED-AIR MOTOR [76] Inventor: Karl Attinger, Seestr. 21,

Holzmaden, Germany [22] Filed: Oct. 2, 1972 [21] Appl. No.: 294,206

[30] Foreign Application Priority Data Oct. 1, 1971 Germany 7137280[U] U.S. C1. 5 l/l70 TL Int. Cl B24b 23/04 References Cited UNITED STATES PATENTS 3/1950 11/1952 Martin 51/170 TL 23 ZSIISIDIJ HAND GRINDER WITH A DRIVE MOTOR, I

Field of Search 51/170 R, 170 TL, 170 MT Smu1 51/273 3,527,111 Zimmerman 51/171111 9/1970 3,535,983 10/1970 McHenry 3,638,362 2/1972 StOll 3,788,011 1/1974 Hutchins 51/170 R Primary ExaminerA1 Lawrence Smith 1 Assistant ExaminerMarc R. Davidson [57 ABSTRACT A hand grinder driven by a compressed-air motor has attached on the work-engaging side thereof a hollow workplate, which carries on its underside a cover plate under which bears an abrasive sheet. Suction for-the removal of grindings is provided by means of a duct terminating at one end at the handle in a connection for a suction device and passing through the grinder to the hollow workplate, from which openings to the grinding surface pass through both the cover plate and the abrasive sheet.

1 I 3 Claims, 6 Drawing Figures PATENTEL DEC 7 I974 snmau sg PATENTELIE] 119M 3,854,897

sum 3 or 5 PATENTEL DEC 7 I974 suasruu g gy P19. 4

PATENTEJ 3.854.897

snmsu 5 HAND GRINDER WITH A DRIVE MOTOR, DESIGNED AS A COMPRESSED-AIR MOTOR The invention relates to a hand grinder with a drive motor, designed as a compressed-air motor, in a casing on which is suspended a workplate, driven by the motor, contained in one plane and carrying out oscillating movements, said workplate carrying at the foot a cover-plate on whose underside there is provided a grinding means, formed for example as an abrasive sheet or abrasive cloth, the upper side of the casing being designed as a handle.

Hand grinders of the type in question here, operated by a compressed-air motor, have the advantage that they are cheaper to manufacture, the construction of the motor is simpler, and servicing is simpler and cheaper. These implements are robust and powerful, can always be set to work immediately, need practically no repairs, and can also be kept in explosion-risk areas. The object of the present invention is to design devices of the type in question in such a way that the removal of the grinding waste can be simply carried out with the maximum efficiency and to facilitate the working of chamfered edges, corners and other contours which are not as a rule easily accessible.

For the above purpose provision is made, according to the invention, in the new hand grinder forit to have a suction device for removing the grindings, the cover plate having passing through it several openings also passing through the grinding means, and opening downwards and towards the underside of the workplate, the said workplate having passing through it a hollow space extending substantially over its entire surface area, said hollow space connecting at one end with the passage openings and at the other end, via a suction opening, with the suction device which consists of a separate suction device driven independently of the grinder, said suction device being connected to the workplate by a flexible suction pipe.

The device according to the invention has the advantages that the edge of the grinding paper can penetrate into the angles, corners and the like, and the suction power is substantially increased due to short suction paths which result when grinding flat surfaces and even curved surfaces.

Preferably the inlet for compressed air to the compressed air motor, and other hand ducts for selective connection to the suction device or to a fluid-supply device or a water pipe are located in the handle, said ducts passing through the handle and opening into the interior of the casing. This arrangement has the advantage that the device can be very rapidly 'used, without much outlay, both for finishing grinding, and also for dry grinding with optional connection to a suction device.

In all, a device results which can be used in many ways, that is, with suction removal of grindings, or if necessary without such removal, with the possibility of finishing grinding, etc.. As a result of its considerable advantages, the device is also usable for coachwork.

An embodiment of the invention will now be de- FIG. 4 is a partial section along line B-B in FIG. 5 seen in direction D of FIG. 2, through the handle of the hand grinder; I FIG. 5 is a view of the handle seen in direction C of FIG. 4; and

FIG. 6 is a view from below of the workplate of the.

hand 1 grinder. I

As is visible in particular from FIGS. 1 and 2, the hand grinder consists of a casing l and a handle 3 connected to casing l by screws 2. This handle 3 is shown separately in FIGS. 4 and 5, FIG. 4 beinga view of the handle 3 in direction D of FIG. 2. The design of this handle 3 will be discussed in more detail below.

Beneath casing 1 there is arranged the workplate 4, connected to the casing 1 by four rubber elements 5. Workplate 4 has a hollow space on its underside. It also carries on its underside a'cover plate 7, preferably consisting of an elastic material, on whose underside the grinding means (not shown) bears. The grinding means, for example a grinding cloth, is secured at both ends by pivotally-mounted clamp strips 9 attached under spring tension (springs 8) to the workplate.

The hand grinder is driven by a compressed air motor 10, consisting of a rotor- 12 mounted eccentrically. relative to the bore in the rotor casing 11 containing it. The rotor 12 is cylindrical in shape with several wings 13, which move radially outwards, and which in this way bear with their outer edges on the wall of the rotor casing bore.

The rotor 12 is wedged on 'to a shaft 14 (for example by means of the locking spring 15). On the end facing away from rotor 12, the rotor shaft 14 carries an eccentric l6, engaging in an opening in the workplate 4 and a bearing 17 is arranged in the workplate 4 to accommodate the eccentric l6. Bearing 17, which can be formed as a roller bearing, is surrounded by a bush 18, which carries on one side an annular-shaped sealing lip 19. This sealing lip 19 bears on a bush 20 pushed on t eccentric 16, providing a seal.

The rotor shaft 14 is connected to balance weights 21 and 22, which are provided to compensate for the inertial forces caused during rotation. The rotor 12 itself is arranged between two cover discs 23 and 24. These cover discs 23 and 24 bear on the end surfaces of rotor 12. The cover disc 23 also acts'as a bearingcover for one of two roller bearings 25 and 26.

The handle 3 of the hand grinder will be discussed in more detail. Several ducts pass through the handle 3, two of these ducts, that is duct 27 for supplying the compressed air to the compressed air motor, and duct 28 for supplying a fluid, for example water, lie adjacent to one another at roughly the same height. Ducts 27 scribed by way of example with reference to the draw- FIG. 3 is a section along line A-A of FIG. 2;

and 28 are circular in cross-section. Beneath ducts 27 and 28 there is a further duct 29 which is of greater width than height, and whose width is preferably twice to three times the diameter of ducts 27 and 28. This duct 29 is intended for connection to a suction device;

it serves to remove grinding waste which arises during dry grinding of the workpiece to be ground. The external mouths of ducts 27 to 29 all have rounded nozzles 30 to 32 which are shown in FIGS. 1 and 2, whereby the ducts 27 to 29 can be connected to their respective devices by means of appropriately designed hoses (not shown).

As shown in particular in FIG. 3, both the duct 27 for supplying compressed the duct and theduct 28 for supplying water have associated with them manually operated valves 33 and 34 respectively. These valves 33 and 34 are designed as spring-loaded non-return valves. The valve closure members 35 and 35 are designed as balls which are biased by springs 36 or 36' which attempt to close the valve closure members 35 and 35' to form seals, the closure members being connected to rods 37 or 37 which are supported on a hand lever 38. The longitudinal axes of rods 37 and 37 coincide or approximately coincide with the line of force of springs 36 and 36', which are designed as pressure springs. The rods 37 and 37 have increased diameter portions 39 and 39 respectively at theends facing hand lever 38, these increased diameter portions being guided in bushes 40 or 40. The bore diameters of bushes 40 and 40' are slightly larger than the diameter of the increased diameter portions 39 and 39' by an amount necessary to allow relative sliding movement. When the hand lever 38 is actuated, rods 37 and 37 are pushed towards the valve closure member 35 and 35' so that said member 35 and 35 are raised from their valve seats against the action of springs 36' and 36, hence opening the non-return valve 32 and 34.

Attached to handle 3 is a tube 41, which projects into the interior of the handle. Tube41 has a closed base. It is connected by a branch. duct 42 to the duct 28 for supplying water or another fluid suitable for finishing grinding. In the vicinity of its base, tube 41 has two water distributors 43 and 43'. These distributors 43 and 43 are tubular in shape and first extend laterally outwards in mutually opposite directions, and then run, in the region of the edge of easing 1, roughly parallel to its longitudinal edges. The water distributors 43 and 43' in this case lie in a plane roughly parallel to the workplate 4. The portion of waterdistributors 43 and 43 lying in the region of casing 1 carries fine jet-like openings (not shown in the drawing), allowing passage to the water of fluid to be applied to the workpiece to be ground.

The compressed air duct 27 opens into a jet 44 (see FIG. 2, in which jet 44 is shown in dotted lines), which is connected to the bore of the rotor casing 1 l by a corresponding bore 45.

The duct 29 for suction removal of the grindings arising during dry grindingis connected to the hollow space 6 of workplate 4 by a hose 46, so that the grindings can be sucked out laterally through hose 46 and duct 29.

It is thus possible to change rapidly from one type of be carried out, the device is not connected to a water pass through the branch duct 42 to the water distributors 43 and 43.

Finally, the device can be connected to a compressed air source only, so that dry grinding is effected without suction removal of the chips.

As can be seen in FIG. 1 the cover plate 7 has several openings 50 passing through it. These openings also pass through the grinding means, which can for example consist of a grinding sheet or a grinding cloth, and

open downwards towards the underside of thelwork plate. The workplate has passingthrough it a hollow space 6, extending over its entire. surface area, said space connecting the openings 50 to a suction opening 51. The suction opening 51 is connected to the suction opening of the workplate by the flexible hosepipe 46 and the duct 29. Hose 46 leads m the passage duct 29,

which can be connected to theseparate suctiondevice by the connector nozzle 32. This connector nozzle 32 consists of plug-in portion 53, which is insertable from the front of the device into the associated duct, and which can be fixed in position by-a pin 52. The plug-in portion 53 can beof a special shape, for example tri-- angular in cross-section. The connector nozzle 32 further consists of a connector portion 54 projecting out of the casing, to which the pipe leadingto the suction device, for example ahose, can be connected. When the suction device is connected, the grindings, dust, etc. are sucked through openings 50 in the cover plate 7, through the hollow space 6 in the workplate 4,

through hose 46, which is connected to openingsSl, through pipe 29 and connector nozzle 32, hence passing to the suction device connected to the nozzle. In order to obtain favorable flow conditions, the hollow space 6 on the underside of the workplate 4, as shown in FIG. 6, is divided into ducts 58, 59, 60, 61 by partition walls 55, 56, 57 extending longitudinally along the plate, said ducts 58 to 61 being interconnected by apertures 62, 63, 64. A roughly rectangular aperture passes "through the central region of the plate and forms the opening 51 to which hose 46 is connected; The .ducts on the underside of the workplate taper towards the end at which the roughly rectangular aperture passes 9 through the workplate, that is tapering in the direction of arrows 65, 66, and this facilitates the flow of grindings to the opening 51, The cast recesses are smooth in I construction, so that no flow losses'occur; this applies both to the recesses in the workplate and to those in the -handle casing. The flexible connection between the supply but is connected to a compressed-air supply for actuating the motor and to a suction device. When hand lever 38 is actuated, valve 33 opens, allowing compressed air to reach the motor. Valve 34 also opens, as it is actuated synchronously with valve 33 via hand lever 38, but no water is supplied, as the device is not connected to a water pipe. The grinding waste occurring during dry grinding being thus removed by the separate suction device (not shown) which is connected to nozzle 32. e

if the device is to be converted to finishing grinding, nozzle 30 is connected to the water pipe and the suction removal is disconnected from nozzle 32. As soon as the hand lever 38 is actuated, and compressed air flows to the motor, so that the latter sets the workplate 4 in motion, valve 34 opens and the fluid or water can movable workplate and the casing formed by hose 46 prevents any damage in the air supply as a result of the unavoidable vibration.

What I claim is: l. A hand grinder comprising a casing, a work plate,

a means movably supporting the work plate on the casing for oscillating movement with respect thereto substantially in a single plane, a-compressed air motor carried by the casing and connected to the work plate for imparting such movement thereto, said work plate having secured on its under side a cover plate, means to secure a grinding means'on the underside of the cover plate, the casing having an upper part constituting a handle, means forming a suction passage in the casing for sucking out waste produced by the grinding means, said passage extending to the outside of the casing for connection to a separate suction device driving independently of the grinder, the cover plate having a plurality of openings therethrough opening through the bottom 2. A hand grinder as claimed in claim 1 having a flexi-- ble hose (46) connecting the hollow (6) on the underside of the work plate (4) and extending between the casing handle (3) and the work plate (4).

3. A hand grinder as claimed in claim 1, in which the ducts on the underside of the work plate in the central region taper inwardly in the direction of the suction opening. 

1. A HAND GRINDER COMPRISING A CASING, A WORK PLATE, MEANS MOVABLY SUPPORTING THE WORK PLATE ON THE CASING FOR OSCILLATING MOVEMENT WITH RESPECT THERETO SUBSTANTIALLY IN A SINGLE PLANE, A COMPRESSED AIR MOTOR CARRIED BY THE CASING AND CONNECTED TO SAID WORK PLATE FOR IMPARTING SUCH MOVEMENT THERETO, SAID WORK PLATE HAVING SECURED ON ITS UNDER SIDE A COVER PLATE, MEANS TO SECURE A GRINDING MEANS ON THE UNDERSIDE OF THE COVER PLATE, THE CASING HAVING AN UPPER PART CONSISTTUTING A HANDLE, MEANS FORMING A SUCTION PASSAGE IN THE CASING FOR SUCKING OUT WASTE PRODUCED BY THE GRINDING MEANS, SAID PASSAGE EXTENDING TO THE OUTSIDE OF THE CASING FOR CONNECTION TO A SEPARATE SUCTION DEVICE DRIVING INDEPENDENTLY OF THE GRINDER, THE COVER PLATE HAVING A PLURALITY OF OPENINGS THERETHROUGH OPENING THROUGH THE BOTTOM THEREOF AND UPWARDLY INTO THE AREA OF THE WORK PLATE, THE WORK PLATE HAVING A HOLLOW ON THE UNDERSIDE THEREOF EXTENDING SUBSTANTIALLY OVER ITS ENTIRE SURFACE AREA AND COMMUNICATING WITH THE OPENINGS IN THE COVER PLATE, AND THE HOLLOW SPACE HAVING A SUCTION OPENING CONNECTED TO THE SUCTION PASSAGE, AND PARTITION WALLS EXTENDING LONGITUDINALLY ALONG THE PLATE DIVIDING THE HOLLOW INTO DUCTS, APERTURES IN THE PARTITION WALLS CONNECTING SAID DUCTS, THE CENTRAL REGION OF THE PLATE CONTAINING SAID SUCTION OPENING AND A FLEXIBLE HOSE (46) CONNECTING THE SUCTION OPENING TO THE SUCTION PASSAGE (29).
 2. A hand grinder as claimed in claim 1 having a flexible hose (46) connecting the hollow (6) on the underside of the work plate (4) and extending between the casing handle (3) and the work plate (4).
 3. A hand grinder as claimed in claim 1, in which the ducts on the underside of the work plate in the central region taper inwardly in the direction of the suction opening. 